


The Experimental Subject

by HazelBeka



Category: Naruto
Genre: Alternate Universe - Canon, Campy Horror, Enemies to Lovers, Found Family, Kidnapping, M/M, Mad Scientists, Now Includes ART!, The family that slays together stays together, dark but also soft, seals master Iruka, villain Anko, villain Iruka, villain Tenzou
Language: English
Status: Completed
Published: 2021-02-08
Updated: 2021-02-08
Packaged: 2021-03-14 07:27:49
Rating: Teen And Up Audiences
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 9,486
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/29292102
Author URL: https://archiveofourown.org/users/HazelBeka/pseuds/HazelBeka
Summary: Iruka is a mad seals scientist carrying out his experiments deep in the wildest part of the woods. Trained by Orochimaru, he’s a missing nin who leaves no trace of his crimes – and no survivors.Kakashi is his latest victim, lured to the lab so that Iruka can finally get his hands on a sharingan. He knows that if he doesn’t escape he may never go home again, but Iruka has two powerful teammates, years of practice, and a disarming smile.It doesn’t sound like the start of a love story, but stranger things have happened.
Relationships: Hatake Kakashi/Umino Iruka, Iruka & Tenzou & Anko
Comments: 24
Kudos: 134





	The Experimental Subject

**Author's Note:**

  * For [MyThoughtBubbles](https://archiveofourown.org/users/MyThoughtBubbles/gifts).



Kakashi did not often get lost in the woods. It was inevitable on some occasions: the forests that covered great swathes of the Land of Fire were in places so thick they were almost impenetrable, and at night especially it was difficult to tell direction when the trail markers were lost to the darkness. Usually, Kakashi would rely on his ninken, but the rain had been falling steadily for hours and had washed away any scents that might have helped them.

He knew he should set up camp and wait for daylight to guide him, but he was almost certain he was being tracked. The feeling had come on at dusk when the light was already too dim to see by and the thousand tiny movements of the forest had taken on a sinister turn. Had the cracking branch been an animal? The rustle of leaves a bird? The steady patter of the rain had obscured the sounds of anyone trying to be careful, but Kakashi listened to his instincts more than his ears, and the prickling on the back of his neck was enough to chase him onwards into the night.

Perhaps because he was so focused on what might be behind him, he didn’t notice the building until he stumbled into a clearing and found it right in front of him. It wasn’t large: a two-storeyed wooden cottage shut up tight against the cold and the dark. There weren’t any lights or signs of life, and Kakashi stood very still staring at it for some time as the rain slid down the back of his neck and seeped a little further through his clothes.

It looked like one of the Konoha safehouses but in the gloom he couldn’t swear to it. He weighed up the risk of using a light, decided that if his pursuer truly existed and had tracked him this far in the pitch black then it would make little difference. If this was a safehouse, it would provide defensive measures as well as shelter him from the weather, and after hours of travelling, he was too tired to pass this up.

He cast a fire jutsu, and a ball of flame burst to life over one upturned palm. It hissed in the rain but he sheltered it with his other hand and it didn’t go out as he raised it towards the cottage and squinted through its meagre light.

He could tell now that the windows were covered by shutters and there was a chimney in the roof producing no smoke. If there was anyone inside, they were likely sleeping but there was only one way to check. Kakashi really didn’t want to knock on the door, but he also didn’t want a sleepless night trudging through the rain and jumping at every sound, so he made sure he had a few weapons in easy reach and then approached the cottage.

It was only because he was feeling so paranoid that he noticed the tiny movement above the door. Kakashi froze just as some ward was activated and a barrier materialised around the house, cutting him off from it. The sound of the rain changed, now a drumming on the hard surface of the barrier, but Kakashi was still staring at the thing above the door. It couldn’t be what he thought it was. He raised his hand until the flame’s orange glow flickered across it.

There was an eye inset into the wood above the door. Kakashi could just make out the complex seals carved around it, so complicated that they stretched all the way down either side of the doorframe and branched off widely so that the door was surrounded by a dark halo of symbols. The eye was pointing down, watching him. From inside the house came footsteps, and then the sound of a bolt being drawn back, and the eye swivelled down as though it wanted to see who was about to step outside.

A man opened the door. A dim light followed him out, and Kakashi glimpsed a living space behind him, a lamp lit on one of the tables, although he couldn’t tell for sure if anyone else was sitting in the shadows. The man in the doorway was solidly built, about Kakashi’s own age, and had eyes so dark they were almost black. He was wearing casual clothes: loose pants and a sweater. No hitai-ate, though Kakashi was almost certain he was shinobi. He didn’t know why; something about the way the man carried himself and the fearlessness with which he glanced over Kakashi, as though he was used to strangers arriving with flames in hand and metal glinting at their belt.

“Nice security system,” Kakashi said. “Whose eye is that?” He was tense, ready to push more chakra into his fire jutsu. In his experience, decent people didn’t have eyeballs in their doorways, but then he had someone else’s eye in his face so he was willing to suspend judgement.

“I don’t remember her name,” the man said. “It’s been a while since she was here. Alive anyway.” He looked past Kakashi and raised his voice, calling into the darkness. “Hey, Anko, you remember what the Hyuuga girl was called?”

Kakashi whirled around in time to see a woman melt out of the trees. Her hair was tied into a ponytail but loose strands were plastered to her face. Her clothes were just as soaked as his, and he knew in his gut that she was the one who’d been trailing him.

“Shit, I don’t know,” she said. “Ask Iruka. He writes that stuff down.” Behind her, Kakashi thought he saw something moving through the trees: something large and sinuous like a snake, but far larger than a snake had any right to be.

“Who are you?” Kakashi asked, voice tight.

The man was still safe behind the barrier, but the woman – Anko – was exposed. He was already planning the attack he’d throw at her and the direction he’d run. Maybe he could take them both on, but he didn’t like how calm they were. How practised this felt. If they truly had killed a Hyuuga – and he thought it was true, remembered a woman who’d been presumed dead on a mission a couple of months ago – then they must be powerful.

“You ever hear stories about monsters in the woods?” the man in the doorway said.

“Yeah, I’ve been in a few of those stories,” Kakashi said. “Slaying the monsters.”

Anko let out a bark of laughter. “Tenzou, I like this one. Can we keep him?”

“You’ll have to ask Iruka,” Tenzou said. “Let’s hurry up and get him inside. It’s cold out here.”

Kakashi took that as his cue. He blasted a stream of fire at Anko, who threw herself to the ground to avoid it, and darted away, sprinting for the treeline.

He didn’t make it.

There was a rustling, slithering sound, and he thought at first it must be the giant snake, but then he saw that the trees themselves were moving. No, something was growing up around them, filling all the spaces between them. Great vines, as thick as his arm and studded with thorns, were bursting from the ground and tangling themselves around the clearing on every side, sealing it off like a razor wire fence, higher and higher.

Kakashi swore and whirled around, catching a glimpse of Tenzou with his hands together, casting the jutsu, but before Kakashi could form a new plan, the snake was on him.

It must have been fast to escape the wall of thorns, and it was certainly strong. Kakashi wished for his ANBU armour, though as the snake snapped his jaws right beside his leg, he considered that even that wouldn’t be enough to protect him. If those teeth closed on a limb, it wouldn’t be a bite: it would be an amputation. Kakashi was so busy avoiding the jaws that he lost track of the snake’s other end until something large and heavy crashed into his back and sent him sprawling to the ground.

“This is really too easy,” Anko’s voice commented from somewhere above him. She sounded like she was on the edge of sulking. “I really thought you’d be more fun to play with, Sharingan Kakashi.”

Kakashi lifted his head, still winded, and shoved up his hitai-ate. The snake’s tail was still resting on his back, pinning him to the ground, and Anko was standing beside him, twirling a senbon idly between her fingers.

“Call off your snake,” Kakashi rasped, already working on a genjutsu. Her eyes widened as he caught her in the illusion, changing his face for Tenzou’s, making her think he was the one her snake had crushed against the earth.

A boot pressed down on the back of his head, slamming his face into the grass.

“Really, Anko?” Tenzou said as he ground his heel into the nape of Kakashi’s neck. “You know he has a sharingan and what do you do? You stare straight into it like an idiot.” He sounded exasperated.

“Just testing it out for you,” Anko said. “I’ve never seen one in real life before.”

“Sensei had at least five in his lab.”

“Well, yeah, but they were floating in jars. It’s not like anyone was using them.”

Kakashi was struggling to breathe, and he squirmed under Tenzou’s boot. Tenzou relaxed the pressure enough that he could draw in a gasping breath that tasted of mud. One of his arms was pinned beneath the snake but he moved the other slowly towards his flak vest, searching for a weapon.

Anko squatted down beside him and grabbed his wrist. “Oh no you don’t,” she sang. “Time to go beddy bye.” There was a sharp sting on his wrist as she jabbed him with the senbon, and Kakashi swore again into the grass.

“Don’t worry,” Tenzou said mildly. “It’s only a tranquiliser. When you wake up, this will all start to make more sense.”

The last thing Kakashi was conscious of was the weight lifting from his back and Tenzou hauling him over his shoulder, carrying his boneless body away from the wall of thorns and into the house.

  


* * *

  


When Kakashi next regained consciousness, he was lying on his back on a hard surface and his sharingan eye was taped shut. He cracked his other eye open and saw the wooden beams of a ceiling above him, inset with small electric lights. His body felt heavy with the drug still, and when he tried to raise one arm he found it was strapped down at the wrist. He hadn’t really expected to be captured and _not_ tied up, but it was always good to make sure.

Someone was humming nearby. It was the distracted, tuneless hum of a person engaged in their work, and Kakashi turned his head towards it. The room was larger than he’d expected but crammed full of furniture. The walls were lined floor to ceiling with metal shelves, which were so full that Kakashi felt anxious just looking at them. Some of the contents were innocent enough – racks of test tubes, piles of chakra paper, precarious towers of petri dishes – but there were also rows of jars whose contents turned Kakashi’s stomach. Eyeballs with the nerves still attached, human hands and hearts, all suspended in preserving fluids, each jar neatly labelled in calligraphic handwriting. A workbench stretched parallel to the shelves, and Kakashi turned his attention to it instead so he wouldn’t have to think about his own insides and where they might end up.

A man was standing on the other side of the workbench, facing Kakashi but ignoring him in favour of something organic and messy that he had pinned to the table and was carefully dissecting. It was small, but Kakashi could smell the blood from across the room.

“I’ll be with you in a minute,” the man said, not looking up. The tip of his tongue poked out as he concentrated on the flap of skin he was peeling back from the thing on the table.

Kakashi had never had cause to consider what a mad scientist might look like, but if he had then he wouldn’t have pictured this. For starters, the man was very young – younger than Kakashi, though not by much. His hair was braided and fell over one shoulder, tied at the end with a green ribbon, and he was a wearing a lab coat over a pale blue sweater. There was a distinctive scar across his nose, but Kakashi was certain he’d never seen this face before in the bingo book, and that was disturbing. He liked to think that the worst people of the world were unable to hide what they were, but nobody who’d met this man – or Tenzou or Anko – had realised they were monsters. Or, at least, nobody had survived long enough to tell the world.

“Are you Iruka?” Kakashi asked. His throat was dry, but his mask had been removed and the lower half of his face was bare.

The man looked up at him then and smiled. It was a warmer smile than Kakashi had expected from someone who kept a row of body parts in his workroom.

“That’s right,” he said. “I’d welcome you to my home, but honestly, Kakashi, I’m not a very good host.”

It didn’t surprise Kakashi that Iruka and his teammates – friends? cronies? – knew who he was, and he didn’t let the familiarity discomfort him.

“I’d noticed,” he said. “You entertain a lot of guests?”

“Not too many,” Iruka said, looking back down at what Kakashi realised belatedly was a human hand, severed at the wrist and missing most of its skin. “People are boring, on the whole. I have a very particular type.”

“And I’m your type?”

Another smile flittered across Iruka’s lips.

“Oh yes,” Iruka said. “You really are.”

He put down the scalpel and stripped the bloody latex gloves from his hands, leaving them crumpled on the worktop as he rounded the end of the bench and crossed the room to stand by Kakashi’s side. Kakashi tensed, testing his strength against his restraints again. His ankles were strapped to the table as well as his wrists, and when he glanced down he saw that the leather cuffs were reinforced by paper seals.

“They’re unbreakable,” Iruka commented, laying a hand on top of Kakashi’s and fingering the restraint. “Or as close to unbreakable as it’s possible to get.”

“You’re pretty full of yourself, aren’t you?”

“Feel free to prove me wrong.” He waited a beat, raising an expectant eyebrow, but Kakashi didn’t rise to the bait. For all he knew, resisting too hard against the seals could cause him to lose a hand. Iruka might be a smug little bastard, but not without cause.

“Now what?” Kakashi asked.

“That depends,” Iruka said, reaching for Kakashi’s face, his lips quirking in amusement when Kakashi flinched. “How does your eye feel?”

Kakashi’s heart almost stopped. Iruka gently peeled the tape away from his sharingan, making a soothing sound when Kakashi’s eyelashes fluttered wildly against his fingers. There was no pain, nothing felt wrong, and yet – 

Kakashi opened his eye. He could still see, could swivel both eyes up to stare at Iruka’s pleased expression, but only now did he realise that something had changed. The sharingan didn’t activate. There was no sudden drain of chakra, no dormant powers awoken, only the erasure of his blind spot and nothing more.

“What the hell have you done to me?” he asked, and was so caught up in his panic that he didn’t care when his voice cracked.

“It’s OK,” Iruka reassured him, stroking Kakashi’s hair back from his eyes. “It’s nothing permanent. Just a few little seals to turn it off.” He reached over Kakashi to a small table and picked up a hand mirror, which he held over Kakashi’s face. “See?”

There were seals painted in dark red ink around Kakashi’s eye. They were delicately done, the lines more intricate than any seals Kakashi had seen before. He couldn’t begin to understand them, so he examined his eye instead. It looked as normal as he’d ever seen it. As normal as it had been before he’d owned it, back when he’d seen it every day in Obito’s face. It wasn’t even bloodshot.

He had the strangest feeling that Obito was staring out of the mirror at him, and he had to turn back to Iruka to shake it off.

“What did you _do_?” he asked again.

Iruka sighed and put the mirror down. “A lot of very complicated seal work, which you won’t appreciate so I won’t explain it. These seals straddle the precarious balance of allowing enough chakra through your eye to still let you see without allowing the sharingan to activate.”

“You said it wasn’t permanent.”

“It’s henna,” Iruka said. “It’ll stick around for a couple of weeks, then it’ll fade.”

Kakashi’s heartrate came down a notch, but now he was past the initial alarm he was able to use his brain for more than panicking.

“You could have just covered my eye,” he said. “You could have cut it out while I was unconscious. Why go to all that trouble?”

Iruka blinked at him. “I wanted to see if I could.”

Kakashi stared. There was an almost childish curiosity in Iruka’s gaze that belied his intentions; if Kakashi hadn’t seen the eyeball fixed above the door, if he hadn’t been stalked through the forest and captured presumably on Iruka’s orders, he would never have guessed that Iruka was more than the mild-mannered, quietly confident man he appeared to be. The contrast was uncanny.

Iruka leaned over Kakashi again, the end of his plait ticking the hollow of Kakashi’s throat.

“The only sharingans I’ve seen before were grown in a lab by my sensei,” he said. “He had a real fascination with them. I was so disappointed when I heard the Uchiha clan had been all but wiped out – I’d always wanted to see a real one in the flesh, so to speak. The ones my sensei made never worked properly. At the time, we thought the problem was in the eyes themselves and the cloning procedures, but now I wonder if it was the donors. After all, your transplant wasn’t exactly a success either, was it?”

He was gazing at Kakashi’s eye without any sense of awkwardness, as though he was merely regarding an object. Kakashi was used to being stared at, but not like this. He couldn’t say he liked it much.

“Who was your sensei?” he asked.

“Orochimaru,” Iruka said, and Kakashi felt a shock at the name. He hadn’t heard it spoken for a long time, but at one point it had been on everyone’s lips. And everything suddenly fell into place.

“You three were his genin team, weren’t you?” he burst out. “I remember that – he was a jounin-sensei, he took his team with him when he fled the village.” He tensed, the hard surface of the table digging into his shoulder blades. “Is he here?”

Iruka shook his head. “He’s not in the Land of Fire anymore. We had some creative differences and he’s changed careers somewhat, but we still write. He likes to hear about my research. He’ll especially like to hear about you.” His thumb traced the edge of Kakashi’s eye. “Of course, first I need to decide what to do with you. I’ve had a few thoughts but I think I’m slowly changing my mind.”

“From what to what?” Kakashi asked, not entirely sure he wanted to know. He could smell the blood on Iruka’s hand. It didn’t fit the gentleness of his touch.

Before Iruka could answer, a door opened, and Kakashi turned to see Tenzou descending a flight of wooden steps in the corner of the room.

“I thought I’d find you down here,” he said, ignoring Kakashi completely. “Have you even slept?”

Iruka straightened up guiltily.

“Yes,” he said, and it was the most obvious lie Kakashi had ever heard. “Why, what time is it?”

Tenzou crossed the room to stand by the foot of Kakashi’s table, folding his arms across his chest.

“The sun’s been up for over an hour.”

“What? Already?” Iruka glanced back at his half-dissected hand. “I just need to finish that off and then I’ll get some sleep.”

Tenzou snorted and took Iruka by the shoulders, turning him towards the stairs and marching him across the lab. Kakashi lifted his head to watch in bemusement.

“But it’ll only take another twenty minutes,” Iruka whined.

“Should have thought of that before you started.”

“I need to clean it up at least!”

“I’ll do it.”

“And what about Kakashi?” Iruka said as they reached the bottom of the stairs. “I can’t just leave him there, he’s messing up my table.”

“Also this is very uncomfortable,” Kakashi added. “I vote that Iruka should untie me.”

“You see?” Iruka said, nodding vigorously. “Even the experimental subject agrees!”

Tenzou shot Kakashi an unimpressed look. “I’ll put all your toys away,” he said. “Go to bed, Iruka.”

Sighing heavily, Iruka shrugged off his lab coat and hung it on a peg on the wall before making his way up the stairs.

“Don’t hurt him,” he warned Tenzou when he reached the door, and Tenzou waved him off with a flippancy Kakashi didn’t much like considering his attachment to all four of his limbs.

Once the door had shut behind Iruka and his footsteps had moved away across the ceiling, Tenzou slowly returned to Kakashi’s side, gaze contemplative as though he were deciding what he should do about him. Kakashi didn’t much like that look. Iruka may be the centre of this strange group, but Kakashi had a feeling that Tenzou posed the biggest threat should he try and escape. Which of course he was planning to do as soon as the opportunity presented itself.

“Didn’t have you pegged as a mother hen,” he commented.

“Yes, well, someone needs to be,” Tenzou said drily. “I suppose I have you to blame for keeping him up all night.”

Kakashi spluttered. “I didn’t choose to be here! If you’re so concerned about his sleeping habits, maybe you shouldn’t have captured me!”

Tenzou hummed thoughtfully. “You’re right, it’s my own fault. I should have cut out your tongue when I had the chance. He’ll be annoyed if I do it now.” His gaze fell on the row of scalpels lined up beside the dissected hand. “Though it may still be worth it.”

Kakashi knew when to shut up. He didn’t say a word.

“All right, let’s get you into your new home,” Tenzou said. 

He jerked his head towards a corner of the room, opposite the stairs, which had been caged off with wire. It didn’t look particularly sturdy, but it was covered in paper seals, which presumably made up for the lack of proper materials.

Tenzou unbuckled the restraints on Kakashi’s ankles first, then moved up to free his hands. Kakashi lay still and let him, barely daring to believe that Tenzou was just going to let him up without restraining or drugging him again. Yet that seemed to be exactly Tenzou’s plan. Once Kakashi’s limbs were no longer tied down, he calmly stepped back and beckoned for Kakashi to stand up off the table. There _had_ to be a catch, and yet Kakashi couldn’t let this opportunity slip by.

He rolled off the table, landing in a crouch in case an attack was coming, and then brought his hands together to form a substitution jutsu. Nothing happened. There was no spark of chakra in his palms, he certainly didn’t end up nearer the stairs and the exit, which had been his plan, and Tenzou looked entirely unmoved by the whole performance.

“Check your hands,” he said.

Kakashi did, glancing at his palms. Henna seals covered every inch, spilling down his wrists a little way. Fucking Iruka. But he didn’t need to mould chakra to land a punch.

He launched himself upwards at Tenzou, intending to catch him around the waist and take him down, but Tenzou had been ready for him and nimbly sidestepped out of the way, bringing up a knee into Kakashi’s stomach. Winded, Kakashi stumbled away, struggling to breathe and glancing around wildly for something he could use as a weapon. He was forced to duck as Tenzou swung for him, but this gave him a second shot at getting under Tenzou’s defences, and this time he crashed into Tenzou’s legs, taking them both down.

They almost fell into Iruka’s workbench, and Kakashi remembered the scalpels lined up next to the severed hand. He pushed himself up, grinding a booted foot down into Tenzou’s chest to keep him pinned, and groped for a scalpel. His fingers brushed the mutilated hand, but he didn’t have time to be squeamish. Tenzou grabbed his ankle and tugged sharply just as Kakashi got a hand around the nearest blade, sending him sprawling to the floor again but no longer unarmed.

“Iruka’s going to kill you if you fuck up his project,” Tenzou panted, hand still around Kakashi’s ankle. He dragged Kakashi away from the workbench, but let go when Kakashi kicked him in the wrist.

“He’s going to kill me anyway,” Kakashi said, scrambling to his feet and falling back into a defensive stance. “So why not mess up his lab a little while you’re being stupid enough to let me escape?”

Tenzou’s lips twitched up into a smile. “Is that what I’m doing?”

It hadn’t escaped Kakashi’s notice that Tenzou was going easy on him. He hadn’t used a single jutsu, hadn’t drawn a weapon; he’d given himself the exact same handicaps Kakashi had to make it a fairer fight.

“I know when someone’s playing with me,” Kakashi said. “But cats who play with their food often go hungry.”

Tenzou hummed, still smiling. He was enjoying this, the bastard.

There was only one way Kakashi could play this. He needed to lure Tenzou in close enough for him to slice an artery, and he needed to do it while Tenzou was still treating this as a joke. As soon as he got bored or decided Kakashi was a credible threat, it was over. This had been a losing battle from the start, but only if it was a real fight. Maybe not if it was a game.

Kakashi turned and bolted for the stairs. The idea had been that Tenzou would give chase, and in the moment of catching him, Kakashi would strike one well-aimed blow with the scalpel.

But Tenzou didn’t follow. He let Kakashi make it to the stairs, and so Kakashi climbed them two at a time, knowing that he’d made the wrong decision but not understanding why yet. It was too late to go back, there was too much distance between them now for a quick strike, and so he did the only sensible thing and tried to open the door.

It was locked.

More than that, it was warded. Kakashi could feel the prickle of chakra against his hand, buzzing a warning. He hesitated, fingers still curled around the handle, knowing he couldn’t brute force his way through it yet having to resist the urge to try.

He had felt _so close_ , and yet he knew now that even if he’d killed Tenzou, he would still have been trapped in this room with the body, waiting for reprisals.

“Are you ready to get in the cage now?” Tenzou asked.

He hadn’t moved from where Kakashi had left him, and Kakashi understood now what this had been about. Tenzou had wanted him to know how thoroughly powerless he was. Had wanted to break the part of him that was searching desperately for escape.

It had worked better than Kakashi wanted to admit.

“Why are you doing this?” Kakashi asked. “I don’t understand why you would carry on Orochimaru’s work after he kidnapped the three of you. You could have come home to Konoha. You could have run away to live new lives – why, when he gave you freedom, would you choose to be like him?”

He hadn’t really expected an answer, but Tenzou gestured around them to the lab.

“I built this house,” he said. “Not with hammers and nails and carpentry. You saw what I did in the woods – do you know what that was?”

Kakashi remembered the wall of thorns and hesitated only a moment before answering.

“It looked like wood release,” he said slowly. “But unless you’re a Senju – and I think I’d know if you were – then I don’t see how that could be possible.”

“Orochimaru-sensei makes the impossible possible,” Tenzou said simply. “Everything I am is because of him. He made us better than we could ever have been in Konoha – smarter, stronger versions of ourselves. We owe him.”

Kakashi stared at him. “He used you as experiments and you think you _owe_ him?”

Tenzou sighed and crossed his arms.

“If you think you’re the first person to try and philosophise your way out of the lab then think again. Are you going to get in the cage by yourself or do I have to make you?”

Kakashi came back down the stairs. He hated every step, but if Tenzou injured him, it might later turn out to be the difference between death and survival. Giving up for now didn’t mean giving up forever.

“Drop the scalpel,” Tenzou said, and Kakashi obeyed.

He walked into the cage of his own volition, and it felt more like defeat than when he’d been captured the night before. At least then they’d had to trap him, fight him and drug him. Tenzou shut the door behind him and secured it with a simple padlock, but Kakashi could feel the strength of the seals on the wire mesh. He didn’t dare touch them, just in case.

“I’ll bring you some food when I’ve had my coffee,” Tenzou said. He was no longer amused; merely bored. Kakashi was just one more prisoner in a long line of those who had died before. “You should probably get some sleep. I’m sure Iruka is planning another long night for the two of you.”

He left Kakashi alone in the lab, with a little less hope and a little more fear, to await his impending fate.

  


* * *

  


Iruka returned to the lab several hours later. At least, Kakashi assumed several hours had gone by. It was hard to tell in the windowless basement lab where the only light was electric and unchanging. There was a futon in the cage with him but he hadn’t been able to sleep. He’d lain down for a little while and tried, but either the lights were too bright or he was too keyed up on adrenaline and he’d ended up staring at the lab instead, trying to memorise every inch of the room in preparation for his next escape attempt – if he ever got the chance.

He was sitting against the wall, wondering how long it would take before Konoha sent out a search party, when Iruka came back. His hair was still braided, but this time it was damp from the shower, and he was wearing a lavender turtleneck sweater with the sleeves rolled up. Once again, Kakashi was struck by how utterly soft he looked. There was no other word for it. Especially when he yawned, stretched, and gave Kakashi a sleepy smile.

“Good news,” he said as a greeting. “I’ve decided what to do with you.”

Kakashi stood up. His legs ached from sitting in a small space for so long.

“Is that good news for me or for you?” he asked.

“Both of us,” Iruka assured him. He crossed to the workbench – Tenzou had cleared away the dissected hand earlier as promised – and set up a Bunsen burner, then grabbed a kettle and filled it with water from the large, bloodstained sink in the back wall. “I had intended to cut out your eye, but now I think it’ll serve a better purpose if I leave it in your face.”

“Good,” Kakashi said cautiously. “That’s my favourite place to keep it.”

Iruka beamed at him totally without irony, and then placed the kettle above the Bunsen burner to heat. He took a teapot and two mismatched teacups down from their place beside a jar filled with human tongues and then spooned some loose tea into the pot. Kakashi tried not to feel too comforted by the domesticity.

“Remember what I was saying last night?” Iruka said. “That the problem with transplanting sharingan eyes is that the donors’ bodies reject them? I think this is a great opportunity to try and find a solution to that. I have a couple of theories about what could be going wrong, and you’re the perfect subject to use as a test case. If I can make your body accept the sharingan fully then we could test it with lab-grown sharingan eyes.”

Kakashi didn’t know how to feel about any of that. He took a moment to absorb the idea as the kettle whistled and Iruka took it off the burner and filled the teapot.

“You want to fix me,” he said, just to make sure he’d understood Iruka’s intentions correctly.

“When I’m done with you, you’ll be able to switch the sharingan on and off just like an Uchiha can,” Iruka agreed. “How do you take your tea, Kakashi?”

“Black, no sugar,” Kakashi answered automatically. “And what happens once you’ve fixed me? Is that when you cut it out?”

Iruka hummed contemplatively. Apparently he hadn’t thought that far ahead, and Kakashi wished he hadn’t made the suggestion.

“It would be probably be more useful to observe the long-term effects of whatever you do to me,” he said hurriedly. “Set me free, let me use it for a while, check that everything’s in working order. Otherwise how can you really test the results?”

Iruka snorted but he poured the tea and set out the cups in front of two stools before crossing over to the cage.

“Subtly isn’t your speciality, is it?” he said, but he sounded amused. “You do make a good point though.” He reached for the door, pausing with his hand on the lock. “I’m going to let you out now. You can either drink a cup of tea with me peacefully or you can make a fuss and Tenzou will be _very_ angry with you. He’s a little overprotective.”

“I won’t hurt you,” Kakashi said, not entirely sure if he was lying.

“I know you won’t,” Iruka said. “But I’m warning you not to try.”

He opened the door, then turned and went back to the workbench, sitting down on one of the stools and turning to Kakashi expectantly.

Kakashi almost wished he was dealing with more normal enemies. The kind that subscribed to the classic school of villainy and didn’t muddy the waters by offering refreshments as they filled you in on their nefarious plans. On the other hand, if Iruka and his team were the usual sort of villains, they’d have either mutilated or killed him by now. Perhaps he would rather have this bewildering tea party after all. 

He sat down on the other stool and Iruka gave him an encouraging smile.

“Do you treat all your prisoners like this?” Kakashi asked.

“No, they usually scream a lot more,” Iruka said, blowing lightly on his tea. “It makes it hard to have a civil conversation.”

“I bet.”

Iruka was staring at his eye again, and this time Kakashi stared right back. It was strange, having both eyes open. He wasn’t used to it. The last time he’d been able to sit and look at someone like this without draining his chakra was so long ago that he couldn’t remember it.

“I don’t understand you, Iruka,” he said. “When we’re talking like this, you don’t seem like a bad person, and I’m having a really hard time reconciling that with the things I know you’ve done.”

Iruka looked away, wrapping both hands around his teacup and staring down into the liquid. “You’ve barely scratched the surface of the things I’ve done. If you knew the extent of it, you wouldn’t be so confused.”

“You sound like you regret it.”

“I don’t enjoy taking lives,” Iruka said. “But I don’t find it repugnant either. I don’t feel much of anything when I kill. Do you?”

Kakashi opened his mouth to say of course he did, and then he closed it again and gave the question the true consideration it deserved.

“No,” he said, and was disturbed by his own answer. “I’ve killed so many people that their faces blur together. It hasn’t kept me up at night in a very long time.”

Iruka nodded and raised the teacup to his lips, though he was staring through the opposite wall, unseeing the shelves and the detritus of human lives he’d collected over the years.

“The first time I killed someone, it was for Konoha,” he said. “I never met the person who ordered the hit, but I took their money after it was over. Death is a bureaucracy in Konoha – in all the hidden villages. Do you really think that’s so much better than what I do here?”

Kakashi didn’t have an answer. “I’d never really thought about it that way before.”

“No,” Iruka agreed. “You can’t see it from the inside. I only started to question it once I’d left. And I’d love to be able to tell you that I turned my back on killing, decided I was a better person than that. But I’m not. People die all the time, Kakashi, often violently and pointlessly. At least my violence has a purpose. No one who died in this lab died for nothing.”

Kakashi looked around at the equipment. He didn’t understand the use of most of it and probably didn’t want to know.

“What do they die for?”

“For science,” Iruka said. “They’re not the first and they won’t be the last. There have always been people like me, at the fringes of right and wrong, trading lives for knowledge. And when your village leaders find us, they decry us and banish us and execute us – but they read the notes we left behind and they use the things we discovered. How do you think Konoha came by its long lists of forbidden techniques? They might call them forbidden but they still keep our records, and when push comes to shove, they allow themselves the taste of forbidden fruit. That’s how our society works.”

They sat in silence, and Kakashi sipped his tea, allowing his thoughts to settle.

“Why are you telling me this?” he asked finally, and his voice came out gentle as though he were acting as confidant to a teammate or a friend.

“I don’t know,” Iruka said. He fiddled with the end of his plait, twirling it around his finger and then letting it spring free. “Life is very insular here. There’s me and Tenzou and Anko, and there’s a village not too far away where we buy our supplies, but I couldn’t call anyone there a friend. It’s been like this ever since we left Konoha, and I honestly don’t know if it’s got better or worse since Orochimaru-sensei left. I know it can’t be healthy, living so closely with two other people and hurting anyone else who comes too near, but that’s the only way I know.” He leaned his chin on his hand and looked at Kakashi askance. “I don’t know what’s different about you. Maybe nothing is. Maybe I’m just reaching my limit of how much isolation I can take.”

“You could stop,” Kakashi said. “Any time you wanted to, you could just stop. Leave this place, go somewhere else and start again.”

But Iruka was shaking his head.

“We passed that point a long time ago,” he said. “You know that as well as I do. Besides, I enjoy what I do. Don’t you enjoy being a shinobi?”

“I don’t know if ‘enjoy’ is the right word, but I’ve never considered giving it up. If someone offered me the chance to retire and live a civilian life, I wouldn’t take it,” Kakashi admitted.

Iruka gave him a wry smile. There was pain in it, and more honesty than Kakashi was used to seeing.

“Killing is a necessary evil for us both,” Iruka said. “I’m not trying to excuse what I do – I know it’s wrong. But I don’t think being a killer for hire is all that honourable either. You’re free to judge me, but I’m free to call you a hypocrite.”

He drained the rest of his tea and stood up.

“I need to make some preparations,” he said. “I’ll talk you through my plans if you want me to. You don’t have to go back in the cage unless you give me a reason to put you there.”

“I won’t hurt you,” Kakashi said again, and this time he knew he was telling the truth.

Iruka looked at him with something like sadness.

“I wish I could promise the same to you.”

  


* * *

  


It took a week for Iruka to plan out his procedure. Kakashi only knew how much time had passed because Iruka told him. Relying on Iruka’s schedule was a terrible way to track the passing days – he often stayed up all night and then slept until the afternoon, to Tenzou’s continued chagrin – but if Kakashi asked him the date or time, Iruka would tell him, and Kakashi didn’t think he was lying.

He saw Tenzou and Anko infrequently, but sometimes he heard their voices from the house above. The lab was Iruka’s domain, though Tenzou came down sometimes to clean, and Anko came when she was bored to ask him about Konoha. She wanted to know what had changed, what had stayed the same, what it was like to be a proper shinobi. Sometimes she sounded wistful, sometimes only curious. The moods in this house changed like the tides, and Kakashi found his overall impression was of the aftermath of tragedy. Three lonely children had grown up here and had never fully recovered from what they’d gone through. He tried not to empathise with them, and failed.

He tried to escape only once after that first night, and it was even less successful. He couldn’t bring himself to try anything when Iruka let him out of the cage, which he did daily, but one morning when Anko brought him breakfast, he tackled her once she’d opened the door. The idea had been to overpower her and force her to take down the wards, but he barely made it two steps into the room before everything went black, and he never could quite remember exactly what she’d done to knock him out. He hadn’t been allowed out of the cage for two days after that, and when Tenzou had next brought him food, he’d broken Kakashi’s nose and left him dripping blood into his stew.

Kakashi hadn’t even been mad at him. The message was clear: fuck with my family and I fuck with you. For the first time he found himself envious of them. When was the last time he’d felt so protective over another person? Was there anyone still living who would feel that protective over him? Maybe Gai, if Kakashi would only let him close enough, but it was hard – so incredibly hard – to let people close. Humans were so fragile. Iruka was right: they died all the time in pointless, violent ways. Yet Iruka and his team had survived, and their tragedy had kept them together.

When the day came, Iruka let Kakashi out of the cage and Kakashi went willingly back to the table where he’d been strapped on that first night.

“How long is this going to take?” Anko asked. She looked out of place in a lab coat, and she seemed as wary as Kakashi about her role as Iruka’s helper.

“It’ll take as long as it takes,” Iruka said. “You’ll do fine. We’ve gone over this about a hundred times.”

“Why isn’t Tenzou helping you?” Anko whined. “He’s better at this stuff than me.”

“Yeah, why do I get the substandard assistant?” Kakashi added.

Iruka huffed and pressed Kakashi to down onto the table.

“Because Tenzou doesn’t know what my plans are,” he muttered. “And I want to keep it that way. Besides, Anko’s done this before. I wouldn’t let her if I didn’t trust her.”

“I don’t trust me,” Anko announced.

“Stop it,” Iruka snapped. “You’re going to make Kakashi nervous.”

“Too late for that,” Kakashi said.

But he lay down, vaguely wondering if he was crazy or stupid or both, because only a true moron would allow themselves to be sedated in a lab where numerous people had died under Iruka’s scalpel. He didn’t fully understand what Iruka was going to do to him, except that it involved some minor surgery of the chakra pathways around his eyes.

The most ridiculous part of all of this, the true extent of his stupidity, was that somewhere along the way he’d realised he trusted Iruka. He trusted him to do what he said he was going to do, and he couldn’t have said exactly why except that Iruka was bad at lying and he didn’t often seem to bother. If something was going to hurt, he said so. He had told Kakashi the risks and complications in sometimes unnecessary detail. If this was a con, it was the best one Kakashi had ever fallen victim to, and if he never woke up from this procedure, he would have brought it on himself.

Anko had mixed the sedative, and Kakashi at least trusted her to drug him correctly. She squeezed the air out of the syringe and then lowered the needle to his arm. Iruka squeezed his other hand, and Kakashi’s last thought was to wonder if Iruka offered comfort to all of his subjects or if Kakashi was special. He drifted off before he could question why the answer felt so important.

  


* * *

  


It took two weeks for Kakashi to heal after the surgery. For most of that time, his eyes were bandaged or covered in gauze, and the world was dark. Sometimes, when he was alone and the lab was quiet, his whole body would seize in the terror that he had made a terrible mistake. Iruka would find him trembling in the corner and climb into the cage with him to take his hands and tell him over and over that he wasn’t blind and the worst would be over soon. His voice became a lifeline, and his gentle hands guided Kakashi through all the tasks he couldn’t now accomplish alone: helping him eat, bathe, dress. Never in Kakashi’s life had he felt more vulnerable or more cared for.

When the bandages finally came off for good, Iruka sat him on a stool and dimmed the lights so the glare wouldn’t hurt his eyes. It felt strange without the wrappings; Iruka had changed the bandages daily, but the longest they’d been off before had been for the twenty minutes it had taken for Iruka to redo the henna seals halfway through the healing period. Kakashi’s eyelashes fluttered, even the pale light feeling painfully bright, and then he opened his eyes to squint up at Iruka.

“How do they feel?” Iruka asked.

The sharingan was still switched off by the henna seals but Kakashi could see Iruka’s face clearly, maybe more clearly than he’d ever seen it before. He drank in all the things he’d missed while he’d lived in blindness: the warm shade of Iruka’s skin, the softness of his hair, the concern in his eyes. Without thinking, he reached out and touched Iruka’s cheek.

“I want to see the sky,” he said. “Please.”

Iruka hesitated, but then nodded.

“All right,” he said. “All right.”

It had been almost a month since Kakashi had been captured, and in all that time he had never left the lab. Now Iruka took down the wards and let him climb the stairs up into the house. It was late at night, and Tenzou and Anko were sleeping, so they made their way quietly through the dark living room and then Iruka let them outside.

Kakashi stepped out onto the grass and was overwhelmed by the open space. He could barely make out the shapes of the trees but he could smell the forest air, clean and fresh after a rainfall, and he could feel the chill of the breeze on his face, hear the hooting of an owl.

Above him, the sky was a patchwork of darkness and stars. The moon was hidden behind a cloud, but maybe that was just as well. It may have been too bright for him. His eyes already ached.

“How long now?” he asked, still gazing at the stars. “Until you let me go?”

Beside him, Iruka pulled his lab coat tighter around himself to ward off the cold night air.

“Not long,” he said softly. “But it won’t be forever. You know that, don’t you?”

Kakashi looked down at him. It had crossed his mind, of course, that he could leave right now. Iruka was smaller than him and weaker than him, and Tenzou and Anko would be too slow even if Iruka screamed. He could wrap his hands around Iruka’s throat, make it soft and slow or fast and painless. There were a dozen ways he could kill Iruka with his hands alone. He didn’t do any of them.

“Depends how fast I run,” he said. “Are you sure you can catch me twice?”

It was Iruka’s turn to touch Kakashi’s face. His palms cupped Kakashi’s jaw and his thumbs softly stroked Kakashi’s cheekbones. It had been a long time since anyone had touched Kakashi like this.

“I won’t need to catch you if you come back on your own,” he said.

Kakashi didn’t close his eyes when Iruka kissed him. He knew it was wrong to wish he could record this moment with his sharingan, that his stomach shouldn’t flip at the way their lips fit together, and that he shouldn’t find so much pleasure in finally getting to bury his fingers in Iruka’s hair. He knew it was wrong in so many ways.

But it didn’t feel wrong at all.

  


* * *

  


Kakashi woke up at the edge of the forest with a headache and a raging thirst.

“What the fuck did you give me this time?” he rasped, reaching for the canteen Anko was holding.

“Oh, don’t be such a baby,” she said. “You were only out for two hours.”

“Did you drag me out here? I feel like I got smacked in the head.”

Iruka and Anko exchanged a slightly guilty look.

“We might have let Taro carry you,” Iruka said.

“Who the hell is Taro?” Kakashi asked, and then whipped his head around as he heard a loud hiss.

Anko’s oversized snake summons was coiled between the trees, its tongue flicking out as it watched him.

“You weigh a tonne,” Anko said, somewhere between accusing and defensive. “Tenzou’s the one who does the heavy lifting. What, you think could Iruka or I could lug you all the way out here?”

“Are you calling me fat?” Kakashi spluttered.

“Hardly. You’re like a beanpole, all those long, flailing limbs – you could have taken my eye out!”

Kakashi raised an eyebrow at that and she flushed.

“I’m sure Iruka could have fixed you up with a new one,” he said.

It was mid-afternoon and the sunlight was slanting down through the trees. Kakashi’s eyes were no longer light-sensitive, having healed for a few more days before Iruka had decided it was time to set him free. The henna seals were starting to fade, both on his face and his hands, and he could feel the chakra returning to them, like he’d been numb all this time but the feeling was slowly coming back.

Iruka had given him back his mask and his hitai-ate, and he was wearing both. It felt strange to have so much of his face covered. Iruka had also brought his pack, the supplies in them untouched, and he handed it over now. Kakashi slung it over his back, hearing the clink of weapons inside.

There was a reason why Anko’s summons was still here. The same reason why they’d drugged him before taking him out of the forest. He would never find his way back to their hideout; not unless they brought him there themselves. Even now, they were cautious. Kakashi couldn’t help but admire them for it. They had been so careful for so long; this was why no one had ever survived them before, why they’d managed to keep their secrets for all this time.

Setting him free was the riskiest thing they’d ever done.

“Tenzou is going to kill you when we get back,” Anko commented to Iruka. “You know this is stupid, right? So stupid I’m actually kind of in awe of you right now.”

Iruka scowled. “I know,” he said. “But it would have been stupider if I’d let him test out the sharingan at the lab. The only way to get the data I need is by sending him into the field.”

“Tenzou’s going to kill me too,” Anko added. “I don’t know why I’m letting you do this.” She cut a look at Kakashi. “You’re either just as stupid as Iruka or very, very smart, and I wish I knew which.”

“There’s only one way to find out,” Kakashi said.

He glanced through the trees to the road beyond, empty and narrow. He didn’t know yet what he’d say when he made it home, how he’d answer the questions about where he’d been. It would be easy to hide the sharingan, easy to lie.

Just as easy to tell the truth and take what Iruka had gifted him without paying anything back.

Iruka’s hand slipped into his.

“Travel quickly,” he said. “When Tenzou finds out I’ve let you go, he’ll come after you. If he finds you, he’ll kill you. You’re a threat, and he won’t rest until he knows we’re safe.”

“He isn’t wrong,” Anko said. There was a thread of tension in her voice that hadn’t been there before. “Iruka – last chance to change your mind.”

Iruka’s hand didn’t leave Kakashi’s, and their gazes stayed locked.

“I’ll leave you to live your life for a while,” Iruka said. “Go on missions. Spend time with your friends. Do all of the things you’ll miss the most when Konoha stops being home. But don’t get too attached because you don’t belong to them anymore.”

“Do I belong to you?” Kakashi asked.

Iruka squeezed his hand almost painfully. Possessively. Kakashi bottled the look in his eyes, stored it somewhere safe.

“Everything born in my lab belongs to me,” Iruka said. “I _will_ take you back, Kakashi. Unless you come looking for me first.”

Kakashi tugged down his mask and kissed him one last time, ignoring the raspberry Anko blew. Iruka bit at his lips as though he wanted to rip a piece of him off and swallow it down, and Kakashi pressed his tongue into Iruka’s mouth, the tang of blood shared between them. It wouldn’t be hard to develop a taste for it.

“How long will it be until I see you again?” he murmured when he pulled back.

Iruka’s lips quirked up. “It was only a few days ago that you were asking how long before I set you free,” he said. “Don’t worry, my love. The more you test that eye for me, the sooner I can take you back. Go do what you do best and kill for me. As many as you can.”

Kakashi stepped back out of the shadow of the trees. He’d missed sunlight and the freedom to run in whatever direction he pleased, but he knew that it wouldn’t be long before he found himself missing the lab and the chemical scent that stung the inside of his nose. He would find himself missing small spaces and talking to Iruka all night long and the timeless bubble of living his life underground.

It was fucked up, but so was the life he had lived before. He just hadn’t seen it then.

He looked back only once when he reached the road, and saw Iruka watching him from the treeline: the monster in the woods. Then he turned and ran, revelling in the burn of his muscles, until the woods were lost to the distance behind him and he could tell himself, if he wanted to, that he was never going back.

**Author's Note:**

> This is a late birthday present for MyThoughtBubbles - happy birthday! I see your dark Kakashi fics and I raise you dark Iruka, or as dark as I seem able to make him, which is still quite soft lol.
> 
> This was only supposed to be a 2-3K oneshot, yet here we are. I could easily have written another 10K of this at least but I'm reining myself in before I get carried away.
> 
> EDIT - the wonderful, talented [callaina](https://archiveofourown.org/users/callaina/pseuds/callaina) drew some art for this fic and kindly allowed me to embed it. I was definitely influenced by her take on adopted brothers Iruka and Tenzou in her fic [On Falling in Love & Other Curses](https://archiveofourown.org/works/24439987/chapters/58970527) so if you want to see more found family between those two (and some super cute kakairu) then definitely check that out!


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